Question

Which of the following genetic diseases show a criss-cross pattern of inheritance?
(a) Haemophilia and colour blindness.
(b) Haemophilia, colour blindness and hypertrichosis of the ear.
(c) Albinism and sickle cell anaemia .
(d) Klinefelter’s syndrome and Turner’s syndrome.

Answer 1

Hint Inheritance is the transfer of genes or traits from the parents to the offsprings. In the criss-cross pattern of inheritance, a gene is transferred either from father to his daughter or from mother to her son. The sex-linked characters are inherited in this type of inheritance.

Complete answer
The most common example of criss-cross inheritance is X-linked inheritance. X-linked inheritance is seen in haemophilia and colour blindness. Both are X-linked disorders in which the trait is transferred from carrier mother to her son or from affected father to his daughter. The females are not affected by the disease as they have two X chromosomes. They are only carriers of the disease. The males are affected by the disease as they have only one X chromosome.
In hypertrichosis of the ear, the trait is inherited to the son from his father. This is a Y linked trait. This means only males are affected by this trait. Males having this trait have excessive growth of hair on the pinna of the ear.
Albinism is an autosomal recessive genetic disease which is caused by the transfer of albinism genes or traits from both the parents. Albinism mostly occurs in males rather than females.
When both the parents carry the mutated gene that causes sickle cell anaemia are transferred to the child, then sickle cell anaemia occurs. This is a recessive autosomal disease in which the shape of RBCs is changed which results in decrease of surface area and hence, affects haemoglobin.
 Klinefelter’s syndrome is caused due to the presence of an extra X chromosome. It occurs in males. This disease is not inherited.
Turner’s syndrome is caused due to absence of a one X chromosome out of two. It occurs in females. This disease is not inherited.

Thus the answer of the above question is (A) Haemophilia and colour blindness, both are sex linked recessive disease where transfer of genes from parents to sons show criss-cross inheritance.

Note: Autosomal linked means that the gene or trait is linked to chromosomes other than sex chromosomes. Sex-linked means the genes are linked to sex chromosome (X or Y). In recessive conditions, two copies of the affected gene must be present in the child for the disease to occur.